W. O. Crosby—Pinite in Eastern Massachusetts. 117 
greens to a dull grass or olive green. The deeper color seems 
usually to belong to the purer varieties. 
t some points, the paste or cement of the conglomerate 
appears to include much pinite; yet in its purest state this sub- 
stance occurs mainly in the form of pebbles. In either case, 
however, it is always clearly an imported constituent of the 
rock. Although not properly a principal ingredient of the con- 
glomerate, the pinite detritus is scarcely ever entirely wanting ; 
while in several limited localities the rock is mainly composed 
of it; forming a distinct pinite conglomerate. The following 
are the principal localities in the Boston basin where the con- 
glomerate is notably rich in pinite: the north shore of Squan- 
tam; Milton, on and near Central Avenue; several points in 
Newton, especially in the vicinity of Newton Corner and New. 
ton Upper Falls; and along the line of the Sudbury River 
Aqueduct in South Natick. 
The pinite pebbles, probably on account of their inferior 
hardness, being permanently plastic, as it were, are usually 
oping pebbles of harder materials. 
The distinctly stratified rocks of the Boston basin include 
two principal varieties—the conglomerate, or “Roxbury pud- 
ding stone,” and the slate. The volume of each of these varies 
from four hundred or five hundred to perhaps one thousand 
feet; and the former constitutes the lower half and the latter 
the upper half of one continuous and conformable series. 
‘pper or argillaceous member of the formation includes the 
Paradoxides slate in Braintree; and this determines the Pri- 
Mordial age of the entire series. The slate, and more espe- 
cially the sandstone which marks the passage from the slate to 
the conglomerate, is sometimes greenish and evidently com- 
ed in part of the débris of pinite. The sediments in the 
‘asin of the River Parker, some thirty miles northeast of Bos- 
‘on, are also probably of Primordial age; and the conglomerate 
portions are largely, sometimes almost entirely, composed o 
Pinite. Traces of this mineral have been frequently observed 
' the conglomerate of uncertain age skirting the soathern base 
ne. Blue Hills, and extending thence southwesterly to Rhode 
an 
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